In the old days, when a Feng Shui master took on a new disciple, the first lesson he gave was to teach the little guy with yellow hair 黄毛小子 the height of the sky and the thickness of the earth. Hence, to describe someone who is arrogant a fair comment we use the phrase "Unaware of the height of Heaven and the thickness of Earth 不知天高地厚."
The second lesson is "Beyond one sky, there is another sky 天外有天, beyond one person, there is another person 人外有人." This tells us the height of the sky is like the depth of the sea - unfathomable. The second sentence says that no matter how good you are, there is another person whose capability is above yours.
The third lesson is "The sea of learning has no bounds 學海無涯. The only way to reach the shore is being diligent 唯勤是岸."
Confucius said, "To learn without thinking brings confusion, to think without learning leads to danger."
子曰,“學而不思則罔,思而不學則殆."
To learn without thinking is the most common sickness. In the ancient days, people were taught that all stars and planets revolve around the earth and hence Heaven was considered round while Earth square 天圓地方. Today, we all know that our earth together with other planets revolve around the sun and our solar system together with other heavenly systems revolve around a common axis. However, do not learn without thinking to draw the conclusion that "Heaven round Earth square" is wrong. Mathematically, it all depends on the choice of the frame of reference. If we choose the frame of reference with our earth as center, then "Heaven round Earth square" is a good description of what we perceive. The basis of Feng Shui is the Ba Gua and the way Fu Xi drew the Ba Gua was to take what he saw at a distance 逺取諸物 together with what are close to his body 近取諸身. It is quite clear what he chose as the frame of reference.
To understand Zhou Yi and the Appendices, it is important to master the way ancient Chinese was written but it is more important to think to explore what the sages had in mind. For example, the innocent looking paragraph quoted below has been misunderstood by a lot of people who claim to understand the Yijing. The cause is the fact that each Chinese character can take several different meanings. You have to make the right choice using your brain, not your eyes or ears.
The two words 順 and 逆 here have the images of going with the flow and going against the flow. Obviously going with the flow is easy while going against the flow is difficult.
The word 數 appears twice here. The word 數 in 數往者順 has to be compared with the word 知 in 知來者逆. Both words are used as transitive verbs. We cannot literally translate the sentences as "To count what is in the past is following the flow. To know what is in the future is going against the current." This will need further annotation. If we translate the underlying meaning, then it will be like "To tell the past is easy, to know the future is difficult" without sacrificing the original flavour. The word 逆 appears twice also. In "是故《易》逆數也" the word 逆 means against. The word 數 here is a noun which is the short form of the compound noun 命數。It is believed that there is a number associated with each life. This number dictates the entire life of a person. The number is called the destiny number 命數 . However, the Yijing says no. "是故《易》逆數也" means "Therefore, Yi is against the concept of a destiny number that determines the happenings during the life of a person."
Some people believe that Yijing is used to tell the future as written on the rocks but it is simply an utterly wrong idea. Yijing is to tell us what we will encounter in the future but the outcome is not fixed. Yijing does not tell us how we will react to what we encounter in the future. We have our free will to do whatever and this will determine the outcome.